First let's clear up some terminology: Some people make a false
distinction between "analogue teletext" and "digital teletext". This is
incorrect. Both forms of teletext are digital. Much more
accurate terms are, ironically, the seemingly simplistic "old teletext"
and "new teletext". Those are the terms that will be used here.

"Old teletext" is encoded (in digital form) in some of the (normally
off-screen and thus invisible) scan lines at the top of an "analogue"
television picture. It is decoded into text and block graphics by your
television itself, which displays them instead of or superimposes them
upon the picture.

Whether your television decodes and displays teletext (and subtitles) when
you tell it to depends from whether the analogue picture signal that it
receives from your cable decoder box contains the encoded "old teletext"
data in the first place.

For "pass-through" analogue channels, available in a few areas, where you
aren't actually watching digitally transmitted channels at all, the "old
teletext" data will be there, of course, just as they are in those same
channels as received via an aerial. This discussion will not touch
such "pass-through" channels further.

In the case of digitally transmitted channels, whether the signal that
your television receives from your cable decoder box contains the "old
teletext" data is entirely at the whim of the channel provider. If the
channel provider places the "old teletext" data into the picture at
source, your cable box will decode them (since, to it, they are just
another part of the picture), your television will receive them in the
decoded video signal from your cable decoder box, and your television will
thus display teletext when told to.

There is a popular misconception that NTL "strips off" the "old teletext"
data from the picture signal when transmitting them via digital cable. This
is untrue.

In the case of major channels, such as the BBC and ITV channels, Channel
4, Channel 5, and so forth, the channel providers do not add the "old
teletext" data in the first place to the digital feed that they give to
NTL. The data are simply not present at source at all. There is nothing
there in the picture signal for your television to decode because nothing
was encoded. Those parts of the picture are simply empty.

This is because, it seems, the major channel providers agree that devoting
a significant amount of the limited bandwidth that is available to a
digital TV channel signal to encoding "old teletext" data into the picture
signal is a waste of bandwidth that would be far better devoted to
encoding actual visible picture information; especially given that those
channel providers (or, in some cases, the teletext providers to which they
subcontract the provision of their teletext services) provide the much
superior "new teletext" anyway, that anyone capable of receiving
a digital television channel must also be capable of receiving.

As TV channels upgrade to digital transmission, the old analogue-style
teletext services will die off to be replaced by the interactive TV
format. It means the end of Teletext's direct link to ITV and Channel 4,
but means we can offer a better-looking, more reliable service, with
enormous potential.

)

The major channel providers provide separate, different, feeds for digital
and for analogue transmission. You'll notice that what is recived on a
digital transmission is noticably different to what is received on an
analogue transmission. (For example: The BBC channels have different
stills, continuity announcements, and trailers for digital and for
analogue.)

However, minor channel providers often have what is effectively one,
single, feed, with both analogue and digital being taken from a single
source. Most of them don't provide a "new teletext" service. Indeed, few
of them provide even an "old teletext" service. Where the channel
provider does provide "old teletext", the fact that their
analogue and digital feeds are mostly taken from the same source means
that the "old teletext" data are present in the picture signal that is
transmitted digitally. Some examples of such channels are "The Box",
"Kerrang!", and "Paramount Comedy". For these channels, your television
can thus decode the "old teletext" data.

"New teletext" on digital cable is transmitted separately from "new
subtitles". Subtitles are not part of the teletext service. Neither of
them are transmitted in "unused scan lines", because there is no such
thing in digital television transmission. They are interwoven with the
MPEG data stream that your cable decoder converts into the analogue
video/audio signals for your television. They are both decoded into text
and graphics by your cable decoder box, and replace or are superimposed
upon the picture signal that is then passed to your television.

So with the "new" system it is not your television that you have
to instruct to display teletext and subtitles, it is your cable decoder
box.

How one displays "new subtitles" depends from what particular cable
decoder box one has. For some boxes, for example, one presses the
"Settings" button on the remote control (or
"Guide" then Yellow if one has the smaller remote control) to
bring up the settings screen, and switches "Subtitles" from
"Off" to "On".

Of course, you are still subject to the whim of the channel provider as to
whether the "new subtitles" for its programmes are provided or not.
Whilst the major channels provide "new subtitles", the minor channels
generally, and disappointingly, do not.

The same is true of "new teletext". The capability is there for any
channel provider to provide a direct link from its channel to a page on
the "new teletext" service, which will be invoked by pressing the Red
button when viewing the channel. Indeed, the BBC regularly takes
advantage of this capability. It is up to the channel provider to
provide the "new teletext" service and to arrange the Red button link with
NTL.